Field of the Invention
Provided are new oxide materials consisting of delaminated layered zeolite precursors and a method for synthesizing the materials under mild conditions. More specifically, provided is the synthesis of delaminated layered zeolite precursor materials such as UCB-1 to UCB-6 by fluoride/chloride anion-promoted exfoliation.
Description of the Related Art
The emergence of a new class of catalysts consisting of delaminated layered zeolite precursors expands the range of reactions that zeolites can catalyze by providing access for larger reactant molecules. ITQ-2 in particular represents the first example of such a material, and consists of micropores derived from the zeolite precursor material, MCM-22(P), which are imbedded within thin and accessible sheets. See, for example, U.S. Pat. No. 6,231,751. These micropores enable shape-selective catalysis. Other delaminated zeolite materials include ITQ-6 synthesized by delamination of PREFER, and ITQ-18, synthesized by delamination of Nu-6(1). See, for example, Corma et al., “Aromatics Alkylation”, U.S. Pat. No. 6,855,855; “New Aluminosilicate and Titanosilicate Delaminated Materials Active for Acid Catalysis, and Oxidation Reactions Using H2O2”, J. Am. Chem. Soc., 2000, vol. 122, pp. 2804-2809; and Corma et al., “ITQ-18 a new delaminated stable zeolite”, Chem. Commun., 2001, pp. 2642-2643.
The synthesis of ITQ-2 and other delaminated layered zeolite precursors has to-date required a high pH medium during precursor material swelling, typically in the pH range of 13.5-13.8. Based on the high solubility of silica in such basic aqueous solution, proof of partial amorphization of the zeolite precursor layers during delamination is evident via transmission electron microscopy (See Lercher et al., “Chemical and structural aspects of the transformation of the MCM-22 precursor into ITQ-2”, Studies in Surface Science and Catalysis, 142, pp. 69-76) and clearly identifiable Si(OH)2 resonances, which must be due to amorphous silica, in the 29Si MAS NMR spectrum of ITQ-2 (See FIG. 4 in Corma et al., “Characterization and Catalytic Activity of MCM-22 and MCM-56 Compared with ITQ-2”, Journal of Catalysis 2000, 191, 218-224.) This has motivated the search for milder conditions for delamination. While there has been notable success in decreasing the temperature from 353 K (80° C.) to room temperature during swelling, it has been impossible to achieve delamination under these milder conditions, since the material reverts back to the zeolite precursor after acidification of the swollen sample. A delaminated layered zeolite precursor material does not revert back to the layered zeolite precursor after acidification, and does not revert back to the calcined form of the layered zeolite precursor after calcination.
It would therefore be of great value to the industry if a synthesis for a new catalyst material of the class of delaminated layered zeolite precursors is discovered which involves milder conditions, particularly pH. Furthermore, it would be extremely cost effective to circumvent the need for sonication, if possible, when synthesizing a delaminated layered zeolite precursor material, since performing sonication operations industrially is known to oftentimes be prohibitively expensive. Also important is the successful preparation of the oxide material via delamination without the material either reverting back to the layered zeolite precursor after acidification or reverting back to the calcined form of the layered zeolite precursor after calcination.
It would also be of great value to the industry if a synthesis for a new catalyst material of the class of delaminated layered zeolite precursors is discovered which is effective yet flexible in the conditions which can be used for preparing such catalyst materials. An objective of the present invention is to provide a flexible process insofar as it can be used at milder pH values, either in organic solvents or in aqueous solution, and either with or without sonication. This flexibility in process conditions is not possible to achieve with the prior art.